U.S. Pat. No. 6,470,099 discloses a method where a document to be scanned is corner referenced on a transparent platen, with the document's image facing down. The platen defines an X-Y coordinate system. A moving line of light extends in the X direction and illuminates the document's image, line by line, as the line of light moves in the image, line by line, as the line of light moves in the Y direction. The line of light that is thus reflected from the document is sensed by a linear CCD array having a large number of individual sensor cells arranged in a line that extends in the X direction and coincides with the line of light. Multiple reference marks embodied in one or more reflection targets are located at a known position relative to the platen and/or its document referencing corner, to be scanned prior to scanning the document. Sensing of the reference marks enables that the X direction physical position of the CCD sensor array relative to the referencing corner to be accurately determined, and the platen's orientation with respect to the CCD array and line of light. A determination of the platen's orientation can include a determination of the platen's skew with respect to the CCD array and line of light, as well as a determination of the platen's orthogonality with respect to the direction of travel of a carriage which supports the CCD array and line of light.
US 2005/0073728 discloses a CCD array image sensor fixed on a Y-direction stage that is supported on an X-direction stage. When a piezo driver supplies voltage to an X-direction piezo element and a Y-direction piezo element, the CCD image sensor is moved in X and Y directions. The X-direction position sensor and the Y direction position sensor detect the position information of the CCD image sensor in X and Y directions, respectively, and send the position information to the piezo driver. The piezo driver sets a target movement of the CCD image sensor and detects the actual movement of the CCD image sensor from the position information. The piezo driver adjusts the output voltage to the X-direction piezo element and the Y-direction piezo element such that the target movement becomes the same as the actual movement. Thus all scan positions are predetermined and fixed relative to the scanner, and these scan positions are the same each time a new image is scanned.
It remains a problem to provide a method where the movement of an image sensor adjusted by a control system is improved, when the control system is subject to be affected by temperature, humidity, atmospheric pressure, light, etc.